It is known that the water in a lead storage battery is electrolysed at the end of charging and during overcharging and that it is therefore necessary to monitor the level of the electrolyte and to correct it frequently.
A method for limiting the water consumption at the end of charging and during overcharging is to chemically reduce the evolved oxygen on the negative electrode. For electrochemical reasons the rate at which hydrogen is evolved then becomes very low. So-called "sealed" lead storage batteries have been proposed on this principle. They have a limited quantity of electrolyte which is practically completely retained in the pores of the active material and of the separators which are constituted by non-woven fibres of glass, polyester, etc. Such a storage battery includes a vent which permits it to operate at a high internal pressure, thereby increasing solubility of oxygen in the electrolyte and the speed at which it is reduced on the negative plates.
Sealed storage batteries can be provided which have negligable water consumption, but the fact that a limited quantity of electrolyte is used leads to reduced performance during discharge whether slow or rapid. Further, the containers of these storage batteries must be mechanically reinforced to enable them to stand up to their high internal pressure.
Preferred embodiments of the present invention provide a lead storage battery whose electrolyte is not so limited and which evolves little gas.